JP3409418B2 - Differential limit torque control device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a differential limiting torque control device for electronically controlling a slip state of a turning outer wheel to an optimum state by a differential limiting torque applied between left and right driving wheels.

[0002]

2. Description of the Related Art Conventionally, as a differential limiting torque control device for electronically controlling a slip state of a turning outer wheel to an optimum state by a differential limiting torque applied between left and right drive wheels, for example,
The one described in JP-A-2-155842 is known.

According to the above-mentioned conventional sources, the target outer wheel slip amount, which increases in accordance with the accelerator increase amount during turning, within a range in which the drive transmission force to the road surface and the lateral force required for turning are maintained. By controlling the differential limiting torque in a direction that coincides with, a technique is disclosed that enables the tail slide amount to be controlled by controlling the accelerator pedal during turning acceleration.

[0004]

However, in the above-mentioned conventional differential limiting torque control device, the start of the outer wheel slip optimized differential limiting torque control for matching the actual outer wheel slip state with the target outer wheel slip state is performed. "When the turning inner wheel speed exceeds the turning outer wheel speed, that is, when the drive inner wheel starts idling", the control ends when "the turning inner wheel speed matches the turning outer wheel speed, that is, the idling of the driving inner wheel converges. When the wheel load of the drive inner wheel is significantly reduced during turning with high lateral acceleration, the control hunting state is created by repeatedly suspending and restarting the differential limit control, which may result in accelerator controllability and drift during cornering. Controllability may be reduced.

That is, when the vehicle is turning at a low speed, the driving inner wheel passes through the innermost side, so that there is a relationship of inner wheel speed <outer wheel speed.
If the differential limiting torque is applied at this time, the differential cannot fully absorb the difference in the turning locus, and a so-called tight corner braking phenomenon appears. The purpose of the limited differential torque control for the outer wheel slip is to prevent the inner wheel from idling during high lateral acceleration turning, thereby increasing the driving force of the turning outer wheel. Therefore, the differential limiting torque control is executed only when the condition of inner wheel speed> outer wheel speed is satisfied. However, when the wheel load of the driving inner wheel is significantly reduced during turning at high lateral acceleration, the left and right driving wheels are directly connected to each other due to the application of a small differential limiting torque, and the inner wheel speed is reduced. = The differential limiting control is interrupted when the outer wheel speed is reached. Then, when the differential limiting torque is released, inner wheel idling occurs again and control is started. By applying a small differential limiting torque, the inner wheel speed = outer wheel speed, and the differential limiting control is interrupted. A hunting state is created in which the differential limiting control is repeatedly suspended and restarted, which causes fluctuations in driving force and steering characteristics.

The present invention has been made in view of the above problems. A first object of the present invention is to electronically optimize a slip state of outer turning wheels by a differential limiting torque applied between left and right driving wheels. In a controlled differential limiting torque control device, it is intended to secure accelerator controllability and drift controllability during cornering when the load on the drive inner wheel is significantly reduced.

The second purpose is to prevent the occurrence of a tie corner brake in addition to the first purpose.

[0008]

In order to achieve the above-mentioned first object, the differential limiting torque control device of the first aspect of the present invention is as follows.
As shown in the claim correspondence diagram, the differential limiting torque applying means a, which is provided between the left and right driving wheels and applies the differential limiting torque according to the control command from the outside, and the drive transmission force to the road surface and the turning. Target outer wheel slip state setting means b for setting a target outer wheel slip state for maintaining a necessary lateral force, left drive wheel slip state detection means c and right drive wheel slip state detection means d for detecting respective slip states of the left and right drive wheels. When,
A turning inner and outer wheel discriminating means e for discriminating a turning inner wheel and a turning outer wheel at the time of turning, and an actual outer wheel slip state for selecting one of the left driving wheel slip state and the right driving wheel slip state as the actual outer wheel slip state by the turning inner and outer wheel identification Selection means f, and outer wheel slip optimization differential limiting torque control means g for outputting to the differential limiting torque applying means a a control command for obtaining a differential limiting torque that matches the actual outer wheel slip state with the target outer wheel slip state. Vehicle speed detecting means h for detecting the vehicle speed,
Left drive wheel speed detection means i and right drive wheel speed detection means j for detecting the respective wheel speeds of the left and right drive wheels, and one of the left drive wheel speed and the right drive wheel speed is determined by the inner and outer wheel identification during turning. The inner wheel drive wheel speed selecting means k to select as and the control for terminating the outer wheel slip optimization differential limiting torque control when the inner wheel drive wheel speed matches or falls below the vehicle body speed during outer wheel slip optimization differential limiting torque control. And a termination means m.

In order to achieve the above-mentioned second object, the differential limiting torque control device of the second invention, as shown in the claim correspondence diagram of FIG. A control starting means n is provided for starting the outer wheel slip optimization differential limiting torque control when the inner wheel speed exceeds the turning outer wheel speed, and the control ending means m is provided when the turning inner wheel speed is equal to or lower than the turning outer wheel speed. In addition, when the inner wheel drive wheel speed is equal to or lower than the vehicle body speed, the outer wheel slip optimization differential limiting torque control is ended.

[0010]

The operation of the first invention will be described.

At the time of turning, a target outer wheel slip state setting means b
At, the target outer wheel slip state is set in which the drive transmission force to the road surface and the lateral force necessary for turning are maintained.

On the other hand, the left driving wheel slip state detecting means c and the right driving wheel slip state detecting means d detect the respective slip states of the left and right driving wheels, and the turning inner and outer wheel identifying means e detects the turning inner wheel when turning. The turning outer wheel is identified, and one of the left driving wheel slip state and the right driving wheel slip state is selected as the actual outer wheel slip state by the actual outer wheel slip state selection means f by the turning inner and outer wheel identification.

In the outer wheel slip optimization differential limiting torque control means g, a control command for obtaining a differential limiting torque for matching the actual outer wheel slip state with the target outer wheel slip state is provided between the left and right drive wheels, and is externally supplied. Is output to the differential limiting torque applying means a for applying the differential limiting torque according to the control command.

Further, in the inner wheel drive wheel speed selection means k, one of the left drive wheel speed from the left drive wheel speed detection means i and the right drive wheel speed from the right drive wheel speed detection means j is identified by the identification of the inner and outer wheels during turning. It is selected as the inner wheel drive wheel speed, and during the outer wheel slip optimization differential limiting torque control, when the inner wheel drive wheel speed matches or is lower than the vehicle body speed in the control terminating means m, the control is terminated.

Therefore, during cornering in which the load on the driving inner wheels is significantly reduced when the vehicle is turning at a high lateral acceleration, the left and right driving wheels are fully differential when a small differential limiting torque is applied by the outer wheel slip optimization differential limiting torque control. Even if the inner wheel slip is suppressed in the limit state, the outer wheel slip is sufficiently suppressed and the inner wheel drive wheel speed does not match with or lower than the vehicle body speed, and the outer wheel slip optimization differential limiting torque control is continued. The change in driving force due to control hunting is suppressed to ensure accelerator controllability, and the change in steer characteristic due to control hunting is suppressed to ensure drift controllability.

The operation of the second invention will be described.

During turning, the outer wheel slip optimization differential limiting torque control is started by the control starting means n when the inner turning wheel speed exceeds the outer turning wheel speed, and by the control ending means m, the inner turning wheel speed. The control is ended when is equal to or lower than the turning outer wheel speed and when the inner wheel drive wheel speed is equal to or lower than the vehicle body speed.

Therefore, even when the target outer wheel slip state and the actual outer wheel slip state are different from each other during turning, the outer wheel slip optimization differential limiting torque control is executed only when the inner wheel idling exceeds the turning outer wheel speed. Will be done,
When turning at a low speed, such as when the inner wheel speed of the turn is less than the outer wheel speed of the turn,
Tight corner brakes are prevented from being generated by applying a differential limiting torque between the left and right drive wheels.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

First, the structure will be described.

FIG. 2 is an overall system diagram of a rear-wheel drive vehicle to which the differential limiting torque control device according to the embodiment of the present invention is applied.

In FIG. 2, 1 is an engine, 2 is a transmission, 3 is a propeller shaft, 4 is an electronically controlled limited slip differential (hereinafter abbreviated as electronically controlled LSD), 5 and 6 are rear wheels, and 7 and 8 are front wheels. Is.

The electronically controlled LSD 4 has a built-in differential limiting clutch 10 for generating a differential limiting torque between the left and right rear wheels 5 and 6 according to the clutch control pressure applied from the hydraulic unit 9.

The hydraulic unit 9 includes a hydraulic power source 11 and an LS.
And a D control valve 12. The hydraulic unit 9 and the differential limiting clutch 10 correspond to the differential limiting torque applying means a.

The LSD control valve 12 is controlled by a control current ICSD from the LSD controller 13 to generate a clutch control pressure for the differential limited clutch 10.

In the active LSD controller 13, the left front wheel rotation speed NFL from the left front wheel rotation sensor 14 and
The right front wheel rotation speed NFR from the right front wheel rotation sensor 15, the left rear wheel rotation speed NRL from the left rear wheel rotation sensor 16, the right rear wheel rotation speed NRR from the right rear wheel rotation sensor 17, and the lateral acceleration sensor 18 From the longitudinal acceleration sensor 19, the longitudinal acceleration XG from the longitudinal acceleration sensor 19, the accelerator opening ACC from the accelerator opening sensor 20, the switch signal BS from the brake switch 21, and the ABS operation signal AS from the ABS controller 22. Is entered.

Next, the operation will be described.

[Differential Limiting Torque Control Operation Processing] FIG. 3 is a flowchart showing the flow of the differential limiting torque control operation processing performed by the active LSD controller 13 at a control cycle of 10 msec. Each step will be described below.

In step 30, the left front wheel rotational speed NFL and
The right front wheel rotation speed NFR, the left rear wheel rotation speed NRL, the right rear wheel rotation speed NRR, the lateral acceleration YG, and the accelerator opening ACC are read.

In step 31, each wheel rotation speed NFL, N
Left front wheel speed VFL, right front wheel speed VFR, left rear wheel speed VRL, and right rear wheel speed VRR are calculated from FR, NRL, and NRR, respectively (left drive wheel speed detection means i and right drive wheel speed detection means). equivalent to j).

In step 32, the vehicle speed VF is calculated from the maximum value of the left front wheel speed VFL and the right front wheel speed VFR (corresponding to the vehicle speed detecting means h).

In step 33, the target outer wheel slip ratio S _A is calculated from the target outer wheel slip ratio characteristic and the accelerator opening ACC shown in FIG. 4 (corresponding to the target outer wheel slip state setting means b).

The target outer wheel slip ratio characteristic is shown in FIG.
As shown in, the accelerator opening ACC is 0 ≦ ACC ≦ ACC1
In the region of, the target outer wheel slip ratio S _A is increased by the proportional gain K _A to about 20% as the accelerator opening ACC increases.
Is given, and about 20 in the region of ACC1 <ACC ≤ 100%
_A constant target outer wheel slip ratio S _A is given in%.

In step 34, the slip ratios S _L and S _R of the left and right rear wheels are calculated by the following equations (corresponding to the left driving wheel slip state detecting means c and the right driving wheel slip state detecting means d).

S _L = {(VRL−VF) / VRL} × 100 (%) S _R = {(VRR−VF) / VRR} × 100 (%) In step 35, the lateral acceleration YG depending on the sensor signal is output. Thus, at the same time as determining whether the vehicle is turning right or left, it is determined which of the left and right rear wheels is the outer wheel turning side (corresponding to the inner and outer wheel identifying means e during turning).

In step 36, it is determined whether or not the left rear wheel speed VRL, which is the outer wheel speed during turning, is less than the right rear wheel speed VRR, which is the inner wheel speed during turning, during right turn (corresponding to the control starting means n).

In step 48, it is judged whether or not the right rear wheel speed VRR which is the turning inner wheel speed is equal to or lower than the vehicle body speed VF (corresponding to the inner wheel drive wheel speed selecting means k and the control ending means m).

In step 37, when VRL ≧ VRR and the condition of VRR ≦ VF is satisfied, a control signal for setting the differential limiting torque to zero to allow the differential between the left and right rear wheels is output.

In step 38, the left rear wheel slip ratio S _L
Is determined to exceed the target outer wheel slip ratio S _A.

In step 39, the left rear wheel slip ratio S _L
And the target outer wheel slip ratio S _A are the same.

In step 40, when S _L > S _A is determined by the determination in step 38, a control signal for reducing the differential limiting torque is output in order to reduce the transmission of driving force to the left rear wheel which is the outer turning wheel. .

In step 41, when S _L <S _A is determined by the determinations in step 38 and step 39, a control signal for increasing the differential limiting torque in order to increase the driving force transmission to the left rear wheel, which is the outer turning wheel, is sent. Is output.

When S _L = S _A , the control signal that is currently being output is maintained as it is in order to maintain that state. By repeating this increase / decrease / holding, the left outer wheel of the turning outer wheel is turned during the right turn. Differential limiting torque control is performed to match the wheel slip ratio S _L with the target outer wheel slip ratio S _A.

Steps 38 to 41 correspond to the actual outer wheel slip state selecting means f and the outer wheel slip optimizing differential limiting torque control means g.

In step 42, it is determined whether or not the right rear wheel speed VRR, which is the outer wheel speed during turning, is less than the left rear wheel speed VRL, which is the inner wheel speed during turning, when the vehicle is turning left (corresponding to the control starting means n).

At step 49, it is judged whether or not the left rear wheel speed VRL which is the turning inner wheel speed is equal to or lower than the vehicle body speed VF (corresponding to the inner wheel drive wheel speed selecting means k and the control ending means m).

In step 43, when VRR ≧ VRL and the condition of VRL ≦ VF is satisfied, a control signal for setting the differential limiting torque to zero to allow the differential between the left and right rear wheels is output.

In step 44, the right rear wheel slip ratio S _R
Is determined to exceed the target outer wheel slip ratio S _A.

At step 45, the right rear wheel slip ratio S _R
And the target outer wheel slip ratio S _A are the same.

In step 46, when S _R > S _A is judged in step 44, a control signal for reducing the differential limiting torque is output in order to reduce the transmission of the driving force to the right rear wheel which is the outer turning wheel. .

In step 47, when S _R <S _A is determined by the determinations in step 44 and step 45, a control signal for increasing the differential limiting torque to increase the driving force transmission to the right rear wheel, which is the outer turning wheel, is sent. Is output.

When S _R = S _A , the control signal that is currently being output is maintained as it is in order to maintain that state, and by repeating this increase / decrease / holding, the right rear wheel of the outer turning wheel is turned during left turning. Differential limiting torque control is performed so that the slip ratio S _R matches the target outer wheel slip ratio S _A.

The steps 44 to 47 correspond to the actual outer wheel slip state selecting means f and the outer wheel slip optimizing differential limiting torque control means g.

[Starting and Ending of Differential Limiting Control] The outer wheel slip optimization differential limiting torque control at the time of turning, if right turning, the condition of VRL (outer wheel speed) <VRR (inner wheel speed) in step 36, That is, the outer wheel slip optimization differential limiting torque control is started in accordance with steps 38 to 41 on condition that the inner wheel idling is started. Similarly, if the vehicle is turning left, VRL (inner wheel speed) in step 42>
Under the condition of VRR (outer wheel speed), that is, the condition that the inner wheel idling is started, the outer wheel slip optimization differential limiting torque control is started in accordance with steps 44 to 47.

During the outer wheel slip optimization differential limiting torque control, if the vehicle is turning to the right, the condition of VRL (outer wheel speed) ≧ VRR (inner wheel speed) in step 36 and VRR in step 48.
(Inner wheel speed) ≤ VF is satisfied, that is, when the inner wheel idling is converged and the inner wheel speed is equal to or lower than the vehicle body speed VF, the outer wheel slip optimization differential limited torque control is performed. Is ended. Similarly, when the vehicle is turning left, when both the condition of VRL (inner wheel speed) ≤ VRR (outer wheel speed) in step 42 and the condition of VRL (inner wheel speed) ≤ VF in step 49 are satisfied, that is, the idling of the inner wheel is If it converges and the inner wheel speed matches or falls below the vehicle speed VF,
The outer wheel slip optimization differential limiting torque control is ended.

As described above, when the inner wheel speed is equal to or lower than the vehicle body speed VF as the ending condition for the outer wheel slip optimization differential limiting torque control, the driving inner wheel load is remarkably increased when turning at a high lateral acceleration. During the decreasing cornering, when the small differential limiting torque is given by the outer wheel slip optimized differential limiting torque control, the left and right driving wheels are in the fully differential limited state and the inner wheel slip is suppressed, but the outer wheel slip is sufficiently suppressed. If the inner wheel speed does not match or is lower than the vehicle body speed VF, the outer wheel slip optimization differential limiting torque control is continued.

Therefore, the control hunting that occurs when the control is ended only by suppressing the inner ring idling as in the conventional device is eliminated, and as a result, the driving force fluctuates due to the control hunting when turning at a high lateral acceleration. The acceleration controllability during cornering is suppressed, and the variation of the steer characteristic due to control hunting is suppressed, and the drift controllability during cornering is ensured.

Further, since the control start condition is the start of the inner wheel idling and the control end condition includes the convergence of the inner wheel idling, the turning outer wheel slip ratio S _L or S _R deviates from the target outer wheel slip ratio S _{A during} turning. Even if it becomes a value, the outer wheel slip optimization differential limited torque control will be executed only when the inner wheel idling when the turning inner wheel speed exceeds the turning outer wheel speed,
At the time of low-speed turning where the turning inner wheel speed <the turning outer wheel speed and the turning inner wheel speed ≦ the vehicle body speed due to the turning radius difference, a differential limiting torque is not applied between the left and right driving wheels, and a so-called tight The occurrence of corner brakes is prevented.

[Differential limit control action during acceleration turn]
A description will be given of the differential limiting control action when the accelerator pedal is depressed to increase the acceleration during the turn.

Initial stage of turning For example, when VRL ≧ VRR in the initial stage of turning right, FIG.
Step 30 → Step 31 → Step 32 → Step 33 → Step 34 → Step 3
The flow proceeds from 5 → step 36 → step 48 → step 37. At step 37, the differential limiting torque is set to zero.

[0061] Further, a right turn early when VRL <VRR is smaller in lateral acceleration YG, the gain K is made to be set to the maximum value K _2, the accelerator opening ACC is smaller in front accelerator depression Therefore, the target outer wheel slip ratio S _A has a small value, the allowable range of the outer wheel slip amount is narrow, and the differential limiting torque is controlled to be low.

Therefore, the slip ratio of the turning outer wheel is suppressed to a small value in the initial stage of turning in any case, and as shown in the characteristics of the cornering force CF in FIG. 5, a high cornering force CF is obtained. The turning stability is ensured.

* Mid-turning In the mid-turning period in which the accelerator depression amount increases from the initial stage of the turning, the accelerator opening degree ACC increases.

Therefore, as is clear from FIG. 4, the accelerator opening ACC increases to 0 as the accelerator opening ACC increases.
In the range of ≤Acc ≤Acc1, the proportional gain K _A gives the target outer wheel slip ratio S _A that increases to about 20% as the accelerator opening ACC increases, and the allowable range of the outer wheel slip amount increases the accelerator opening ACC. Increase accordingly.

Thus, the target outer wheel slip ratio S _A is 0
When increasing from the% side to 20%, as shown in FIG.
The tire-road surface friction coefficient μ tends to increase toward the maximum value, and even if the accelerator opening ACC is in the middle range, the high road surface transmission driving force is maintained on the outer wheel turning side, so that the accelerator opening ACC becomes ACC1. Good acceleration is secured for the accelerator work in the mid range nearby.

Further, in the middle region of the accelerator opening degree ACC, the amount of tail slide flowing outward on the rear wheel side can be controlled by increasing or decreasing the accelerator pedal.

* Acceleration at the corner exit in the latter half of the turn In the latter half of the turn, the accelerator depression amount is further increased in order to ensure acceleration on a straight road from the corner exit.

Therefore, the accelerator opening ACC is ACC1 <
In the high accelerator opening range where ACC ≦ 100%, as is apparent from FIG. 4, a constant target outer wheel slip ratio S _A is given at about 20% regardless of the increase in the accelerator opening ACC, and the outer wheel slip amount is increased. The permissible range is maintained constant regardless of the increase in the accelerator opening ACC.

In this way, when the target outer wheel slip ratio S _A is maintained at about 20%, as shown in FIG.
The maximum value of the road friction coefficient μ is maintained and the cornering force CF on the turning outer wheel side is also maintained at a constant value without decreasing, so that acceleration work increases in the high range of the accelerator opening ACC. The stability of vehicle behavior is ensured without strong oversteering.

Next, the effect will be described.

(1) In the differential limiting torque control device for electronically controlling the outer wheel slip ratio to the optimum state by the differential limiting torque applied between the left and right rear wheels 5 and 6, does the inner wheel speed match the vehicle body speed VF? Since the device is used as the end condition of the outer wheel slip optimization differential limiting torque control when it falls, the accelerator controllability and drift controllability are ensured during cornering where the drive inner wheel load is significantly reduced, such as during high lateral acceleration turning. Can be achieved.

(2) Since the control start condition is the inner wheel idling start and the control end condition includes the inner wheel idling convergence, the occurrence of inner wheel idling during low-speed turning prevents the occurrence of tight corner brakes during inner turning. be able to.

(3) Accelerator opening ACC is 0≤ACC≤ACC
In the area of 1, the accelerator opening ACC by the proportional gain K _A
The target outer wheel slip ratio S increases to about 20% as the
_A is given, and the accelerator opening ACC is ACC1 <ACC ≤ 100%
In this area, a constant target outer wheel slip ratio S _A is given at about 20%, so a constant steer characteristic for accelerator operation is maintained in the high accelerator operation range, and there is no discomfort for the driver and high maneuverability. Is secured. In particular,
In a passenger car or the like where the engine output is not as high as that of a sports car, it is possible to achieve the optimum balance between improved traction performance and improved maneuverability.

Although the embodiments have been described above with reference to the drawings, the specific configuration is not limited to the embodiments, and modifications and additions within the scope of the present invention are included in the present invention. Be done.

For example, in the embodiment, as the vehicle body speed detecting means, the means for detecting the vehicle body speed by the maximum value of the non-driving wheel speed is shown. However, the average value of the left and right non-driving wheel speeds and the integrated value of the vehicle longitudinal acceleration are shown. Etc. may be used as the vehicle speed.

In the embodiment, the example in which the differential limiting torque is applied by the hydraulic multi-plate clutch is shown. However, if the differential limiting torque can be variably controlled by an external control command, an electromagnetic clutch or the like can be used. It may be.

In the embodiment, the example of application to the rear-wheel drive vehicle is shown, but it can be applied to the front-wheel drive vehicle.

In the embodiment, the characteristic shown in FIG. 4 is shown as the characteristic of the target outer wheel slip ratio S _A with respect to the accelerator opening ACC, but the characteristic is not limited to this characteristic, and in the area where the accelerator opening ACC exceeds the normal operation amount area. The characteristic may be such that an increase in the target outer wheel slip ratio S _A with respect to an increase in the accelerator opening ACC is suppressed or a characteristic that the target outer wheel slip ratio S _A is decreased.

For example, in a vehicle equipped with a high power engine, stability is taken into consideration in the medium accelerator region where high output is achieved, and in the high accelerator opening region, cornering force CF is used.
As shown in FIG. 6, the accelerator opening range is set to a low accelerator opening range (0 to ACC2) and a middle accelerator opening range (ACC2
～ACC3) and divided into high accelerator opening region (ACC3 ~), by the proportional gain K _B at low accelerator opening range, also medium-accelerator opening range proportional gain K _C (<K _B), a high accelerator opening In the range, the characteristic of the target outer wheel slip ratio S _A by the proportional gain −K _D may be used.

In the embodiment, the slip ratio is used as the slip condition, but the slip speed (slip speed)
Alternatively, the slip ratio or the slip amount may be used.

For example, when the slip speed which is the difference between the driving wheel speed and the vehicle body speed is used, as shown in FIG. 7, when the accelerator opening ACC is in the range of 0 ≦ ACC ≦ ACC4, the proportional gain K
_A target outer wheel slip speed V _S that increases to V _S max in accordance with an increase in accelerator opening ACC is given by _S , and ACC4 <ACC ≦ 10
In the 0% region, the target outer wheel slip velocity V _S is constant at V _S max.
May be given.

[0082]

According to the first invention of claim 1,
In a differential limiting torque control device for electronically controlling a slip state of a turning outer wheel to an optimum state by a differential limiting torque applied between left and right driving wheels, an inner wheel driving wheel speed is set to a vehicle body during an outer wheel slip optimization differential limiting torque control. Since the device is equipped with a control terminating device that terminates the outer wheel slip optimization differential limiting torque control when it matches or falls below the speed, the accelerator controllability and drift controllability during cornering where the drive inner wheel load is significantly reduced are secured. The effect that it can be achieved is obtained.

According to a second aspect of the present invention, in the differential limiting torque control device according to the first aspect, when the turning inner wheel speed exceeds the turning outer wheel speed, the outer wheel slip optimization differential limiting torque control is performed. A control start means for starting the control is provided, and the control end means optimizes the outer wheel slip when the inner wheel speed during turning matches or falls below the outer wheel speed during turning, and when the inner wheel drive wheel speed matches or falls below the vehicle body speed. Since the means for ending the differential limiting torque control is adopted, in addition to the above effects, it is possible to obtain the effect of preventing the occurrence of the tie corner brake.

[Brief description of drawings]

FIG. 1 is a claim correspondence diagram showing a differential limiting torque control device of the present invention.

FIG. 2 is an overall system diagram of a rear wheel drive vehicle to which the differential limiting torque control device of the embodiment is applied.

FIG. 3 is a flowchart showing a flow of a differential limiting torque control operation process performed by the active LSD controller of the embodiment apparatus.

FIG. 4 is a characteristic diagram of a target outer wheel slip ratio S _A with respect to an accelerator opening ACC in the embodiment apparatus.

FIG. 5: Cornering force CF with respect to slip ratio
FIG. 3 is a characteristic diagram of a tire-road surface friction coefficient μ.

FIG. 6 is a characteristic diagram of a target outer wheel slip ratio S _A with respect to an accelerator opening ACC for a high power engine.

FIG. 7 is an example of a characteristic diagram of a target outer wheel slip velocity V _S with respect to an accelerator opening ACC.

[Explanation of symbols]

a Differential limiting torque applying means b Target outer wheel slip state setting means c Left drive wheel slip state detection means d Right drive wheel slip state detection means e Inner / outer ring identification means when turning f Actual outer wheel slip state selection means g Outer ring slip optimization differential limiting torque control means h Vehicle speed detection means i Left drive wheel speed detection means j Right drive wheel speed detection means k Inner wheel drive wheel speed selection means m Control ending means n Control starting means

Front page continuation (58) Fields surveyed (Int.Cl. ⁷ , DB name) B60K 23/00-23/04 B60K 17/34-17/35 F16H 48/20

Claims (2)

(57) [Claims] 1. A differential limiting torque applying means which is provided between the left and right driving wheels and which applies a differential limiting torque according to a control command from the outside, and a drive transmission force to a road surface and a lateral force required for turning. Target outer wheel slip state setting means for setting the target outer wheel slip state to be kept, left drive wheel slip state detection means and right drive wheel slip state detection means for detecting the respective slip states of the left and right drive wheels, and the turning inner wheel and turning when turning Inner / outer wheel identification means for turning to identify the outer wheel, actual outer wheel slip state selection means for selecting one of the left drive wheel slip state and right drive wheel slip state as the actual outer wheel slip state based on the inner / outer wheel identification when turning, and the actual outer wheel slip Outer wheel slip optimized differential limiting for outputting a control command to the differential limiting torque applying means to obtain a differential limiting torque that matches the state with the target outer wheel slip state Luc control means, vehicle speed detecting means for detecting vehicle speed, left driving wheel speed detecting means and right driving wheel speed detecting means for detecting respective wheel speeds of the left and right driving wheels, and left driving by discriminating inner and outer wheels during turning. Inner wheel drive wheel speed selection means for selecting one of the wheel speed and the right drive wheel speed as the inner wheel drive wheel speed, and when the inner wheel drive wheel speed matches or falls below the vehicle speed during outer wheel slip optimization differential limiting torque control. A differential limiting torque control device, comprising: a control terminating means for terminating the outer wheel slip optimization differential limiting torque control. 2. The differential limiting torque control device according to claim 1, further comprising control starting means for starting outer wheel slip optimization differential limiting torque control when the inner turning wheel speed exceeds the outer turning wheel speed, and the control ends. The means is means for ending the outer wheel slip optimization differential limiting torque control when the inner wheel speed during turning matches or is lower than the outer wheel speed during turning, and when the inner wheel drive wheel speed matches or is lower than the vehicle body speed. A differential limiting torque control device characterized by the above.